While there are a myriad of details for manufacturing paper, the paper manufacturing process conventionally comprises the following steps: (1) forming an aqueous suspension of cellulosic fibers, commonly known as pulp; (2) adding various processing and paper enhancing materials, such as strengthening and/or sizing materials; (3) sheeting and drying the fibers to form a desired cellulosic web; and (4) post-treating the web to provide various desired characteristics to the resulting paper, including surface application of sizing materials, and the like.
Sizing materials are typically in the form of aqueous solutions, dispersions, emulsions or suspensions which render the paper treated with the sizing agent, namely sized paper, resistant to the penetration or wetting by an aqueous liquid, including other treatment additives, printing inks, and the like.
A sizing agent may be applied to the surface of paper as a "surface" size or may be incorporated within the paper as an "internal" size. Various agents are known to be suitable for sizing paper.
U.S. Pat. No. 4,374,673 describes aqueous dispersions which consist essentially of finely-divided fortified rosin particles, a water-soluble or water-dispersible cationic starch dispersing agent for the finely-divided fortified rosin particles, an anionic surface active agent; and water. The aqueous dispersions disclosed therein are used to size paper.
U.S. Pat. No. 4,263,182 describes aqueous dispersions which consist essentially of finely-divided fortified rosin particles; a water-soluble or water-dispersible cationized starch dispersing agent for the finely-divided fortified rosin particles; an anionic surface-active agent; and water. The aqueous dispersions may also be used to size paper.
U.S. Pat. No. 3,966,654 describes essentially stable aqueous dispersions of fortified rosin which consist essentially of fortified rosin in finely-divided form and a water-soluble cationic resin. In an example a water-soluble cationic aminopolyamide-epichlorohydrin resin is shown to be used as the cationic resin. The fortified rosin dispersion is used to size paper.
Canadian Patent Application 746,061 describes paper sizing compositions comprising rosin, and the reaction product of an acidic compound containing a &gt;C.dbd.C--C.dbd.O with a dimer of an acyclic terpene having three double bonds per molecule; the mixture being at least partially neutralised with aqueous alkali. Suitable terpenes include alloocimene, ocimene or myrcene which may be dimerised using phosphoric acid. The acid compounds are .alpha., .beta.-unsaturated carboxylic acids such as maleic or fumaric acid.
Canadian Patent Application 1,045,735 describes a dispersion of enriched rosin containing (A) 5-50 wt % of enriched rosin, (B) 0.5-10% of a water-soluble cationic resin dispersant which is (a) a polyaminopolyamide-epichlorohydrin resin, (b) an alkylene-polyamine-epichlorohydrin resin, or (c) a poly(diallylamino)-epichlorohydrin resin, and (C) water to 100%. The dispersions do not need the addition of (enriched) rosin soap or stabilizers.
Canadian Patent Application 1,057,467 describes the preparation of a stable, aqueous dispersion of a colophony-based material in the presence of an anionic dispersant. The process comprises homogenizing an unstable aqueous dispersion containing by weight, 25-30% solids, consisting, by weight, of 0-95% colophony and of 100-5% adduct of colophony and of an acid compound containing a C.dbd.C--C.dbd.O group. Homogenization is effected under 141-562 atmosphere excess pressure, at 125-180.degree. C. The anionic dispersant may be a saponified colophony-based material, and/or a synthetic emulsifier e.g., alkylaryl sulphonate salt. The dispersion may used in sizing cellulosic fibres for paper manufacture, using "internal" or "external" sizing methods. Paper sheets have improved resistance to penetration of water and aqueous ink.
U.S. Pat. No. 4,983,257 describes an invert size for the engine and tub sizing of paper. It contains an aqueous dispersion of a fortified, unfortified, hydrogenated, or disproportionated and optionally esterified rosin or mixture of such rosins and of a dispersant that contains digested casein or an emulsifier of the general formula (R--(OCH.sub.2 CH.sub.2)n--O--A).sub.x --M.sup.x+ wherein R is an alkylphenyl, alkyl, or alkenyl group or a cycloalkyl group with condensed rings, A is a group with the formula --CH.sub.2 COO or --SO.sub.3, M.sup.x+ is a cation, x is 1 or 2, and n is a number such that approximately 21 to 76% of the molecular weight of the anion is in the --OCH.sub.2 CH.sub.2 group. To allow sizing control, the dispersant contains cationic starch.
European Patent Application EP-A-0686727 describes a sizing material for surface and internal sizing comprising an aqueous dispersion of rosin with starch and a lignin sulphonate. Also described is a process for the production of the size by mixing the rosin with the other components under high shear conditions, such as in a high pressure homogeniser or by stirring with a speed of at least 2000 r.p.m. The document describes a surface and internal size for paper for use in the pH range of 4.5-8.5.
Japanese Patent Application 45-124221 (124221-1970) (Publication No. 49-1247) describes the preparation of an alkyd resin from a rosin, a polyhydric alcohol and an aromatic carboxylic acid.
Japanese Patent Application 3-348085 (348085-1991)(Publication No. 7-120958) describes the manufacture of paper treated with a sizing agent comprising (i) a rosin, (ii) a polyhydric alcohol and (iii) an .alpha., .beta.-unsaturated carboxylic acid derivative, wherein the ratio of hydroxyl group equivalents of (ii) to the carboxyl group equivalents of (i) introduced lies in the range 0.1 to 1.5.
Japanese Patent Application 5-277796(27796-1993)(Publication No. 7-109360) describes production of resin emulsions by emulsifying into water with use of an emulsifier at least one rosin ester, terpene based resin or petroleum resin. The emulsifier is a copolymer produced by copolymerizing (A) 30-70 wt % of styrenes, (B) 10-50 wt % of acrylic acid and/or methacrylic acid and (C) 3 to 20 wt % of sulphonic acid group containing monomer, along with (D) less than 30 wt % of other monomer copolymerizable with (A)-(C). The copolymer has an mw of 2,000 to 100,000, and is used, on a solid basis as its water soluble salt, at ratios of 1 to 20 parts/weight against 100 parts/weight of the resin on a solid basis. The emulsifier permits rosin esters, terpene resins or petroleum resins to be emulsified into emulsions in the form smaller uniform particles, with improved stability and water resistance as well as reduced foaming property, being useful in the production of paints, adhesives, etc.
Whilst many sizing compositions are known there is constantly a need for improved sizing compositions capable of imparting improved print characteristics to paper, for example improved definition and colour integrity from ink jet printers.
There is also a need to provide sizing compositions which facilitate simpler, more economical and environmentally acceptable paper making processes. The manufacture of paper typically involves preparation of a cellulose pulp furnish comprising approximately 99% water, which has to be removed by drainage, suction, pressing and drying. The furnish, successively, flows onto an open mesh wire, where approximately 90% of the water is removed by free drainage and suction, followed by pressing between rollers and finally drying on heated drying cylinders. The water content of the "dry" paper is of the order of 0-10%, typically approximately 5%. The "dry" paper product can undergo further production processes or be reeled and used. Processes at this stage refer to treatments at the "dry end" of the paper machine. Surface sizing refers to the process in which sizing materials are applied to the paper surface in a sizing press at the dry end of the process and may be followed by further drying on heated drying cylinders. The "dry" end of the paper making process refers to the sizing press and subsequent stages of the process. In order to reduce the consumption of water in the paper making process it is desirable to recycle water. Recycling of water, however, leads to a build up of spent chemicals and pulp components (which interfere with sizing) and an increase in water temperature (which accelerates side reactions which interfere with the paper chemicals' normal function). These effects can be reduced by applying sizing agents at the dry end of the paper making process, using size press techniques, e.g., puddle press, coating bill blades and film presses. There is therefore a need for sizing agents capable of application to paper at a "dry" stage in the paper making process.